(a) Field of the Invention
The present invention relates to a method and a system that diagnoses failure of an oil pressure sensor that senses or detects an operating oil pressure in a device (e.g., a hydraulic clutch) using oil pressure.
(b) Description of the Related Art
In general, a transmission, a clutch, and the like are apparatuses that use oil pressure or hydraulic pressure, in which an oil pressure sensor that senses or detects the oil pressure is installed. The transmission, the clutch, and the like are typically applied to a hybrid vehicle as well as a general vehicle.
The hybrid vehicle uses a motor as a power source, as well as an engine. In the hybrid vehicle 1, as illustrated in FIG. 1, an engine 10, a motor 20, and a transmission 40 may be arranged in series. The hybrid vehicle 1 may include an integrated starter-generator (ISG) 70 and an engine clutch 30. The ISG 70 starts the engine 10 or generates electric power by torque of the engine 10, and the engine clutch 30 controls power transmission between the engine 10 and the motor 20. The engine clutch 30 is an element of the hybrid vehicle that is designed to efficiently combine and use power of the engine 10 and the motor 20.
FIG. 2 is a configuration diagram illustrating a typical engine clutch. As illustrated in FIG. 2, the engine clutch 30 may include a friction material 36 moving via pressure by a fluid (e.g., oil) 34 of which a quantity is controlled by operation of an oil pump 50 (or a solenoid valve), and a return spring 32 that restores the friction material 36 to an original state when an operating pressure is not applied to the friction material 36. The oil pump 50 is generally controlled by an applied voltage and/or current. Oil pressure applied to the engine clutch 30 by the oil pump 50 may be detected by an oil pressure sensor 80.
However, as illustrated in FIG. 3, a difference, that is, an error, may exist between an actual pressure detected by the oil pressure sensor 80 and an ideal pressure that corresponds to a voltage applied to the oil pump 50. In the error illustrated in FIG. 3, an offset error, a gain error, and a linearity error may be included. Since the oil pressure detected by the oil pressure sensor 80 is used in controlling the engine clutch 30, when the error as described exceeds a predetermined value guaranteed by oil pressure sensor manufacturers, the oil pressure sensor 80 may be determined to have failed.
When the oil pressure sensor has been determined to have failed, a warning lamp may be turned on to inform a driver of the oil pressure sensor failure and replacement necessity thereof. Accordingly, even when a command for supplying oil pressure does not exist, when the oil pressure sensor 80 detects a pressure that exceeds the guaranteed offset error range set by the oil pressure sensor manufacturers, the oil pressure sensor 80 may be determined to have failed.
In the related art, to determine whether an oil pressure sensor has failed, diagnosing of the oil pressure sensor is implemented when a command for supplying oil pressure does not exist before an oil pump is operated after an ignition on time. The ignition being on means an electrical state in which a hybrid vehicle may be driven by power of a motor.
However, when an ignition is turned on again before a predetermined time passes after the ignition is turned off, the oil pressure sensor may detect a pressure over the guaranteed offset error range due to the remaining pressure in the engine clutch, and thus the oil pressure sensor may be determined to have failed in the diagnosing process. In other words, when a soaking time defined by a time from an ignition off time to an ignition on time is shorter than the predetermined time, the oil pressure sensor may detect a pressure over the guaranteed offset error range due to the remaining pressure in the engine clutch.
It is generally known that the predetermined time is a maximum of 5 minutes. Accordingly, when the soaking time is 5 minutes or more, the remaining pressure in the engine clutch is eliminated. In the related art, when the soaking time is less than the predetermined time, the oil pressure sensor may detect remaining pressure in an engine clutch, and thus the pressure sensor may be diagnosed to have failed.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.